You can try applying the patch from here against qt-core
https://bugs.kde.org/show_bug.cgi?id=311751#c28
(drop it into /etc/portage/patches/x11-libs/qt-core)
It certainly did the trick on my system._________________"The only difference between me and a madman is that I am not MAD" (SALVATOR DALI)

Just for the record, I was hit by this bug as well, and all I had to do to get everything back to normal was to rebuild JUST x11-libs/qt-core with -Os. No need to upgrade qt-core or rebuild other packages.

I finally just re-emerged qt-core and plasma-workspace and things are back. I didn't see whether just qt-core would be enough. I didn't use any special options. Seems like somebody made some improvements...

I'm getting confused here. If I read this thread correctly, to upgrade from KDE 4.9.5 to 4.10.0 yesterday it was necessary to do the following (I've only included the version numbers to avoid any doubt):

I'm getting confused here. If I read this thread correctly, to upgrade from KDE 4.9.5 to 4.10.0 yesterday it was necessary to do the following (I've only included the version numbers to avoid any doubt):

Just out of interest, though, the result would be the same, wouldn't it?

Yes - my given example just illustrate, how to have package-dependend CFLAGS/FEATURES/etc which either just enhances the global flags or will replace them. It is just one convenient way - of many others - Gentoo is just a distribution which gives - in best linux tradition - you the choice.

Looking at Gentoo Bugzilla Bug Report No. 450818 it seems the Gentoo developers will have a solution for the qt-core bug soon, so none of the above will be needed anyway and a KDE 4.9.5 user will then be able to just perform the usual merge of kde-meta or upgrade world in order to upgrade to KDE 4.10.0.

I've already recompiled qt-core using -Os, but I think I'll recompile it with -O2 again and hold off upgrading to KDE 4.10.0 until the developers have found a fix to the bug._________________Fitzcarraldo's blog

Well, I finally bit the bullet, unmasked KDE 4.10.0 and merged kde-meta. Ten hours later the upgrade completed, I rebooted, and everything seems to be working fine. A big thank you to all the Gentoo people who made this possible, especially David E. Narváez for his qt-core patch._________________Fitzcarraldo's blog